Final answer:
The ability of the skin sensory system to distinguish two separate points of touch is affected by the density of nerve endings, which is why the two-point discrimination distance is closer on the fingertips compared to less sensitive areas like the palm, arm, or shoulder.
Step-by-step explanation:
The concept in question relates to the biological phenomenon known as two-point discrimination, which is the ability of the skin sensory system to perceive two distinct points of touch as separate stimuli. The distance at which this discrimination can occur varies across different parts of the body; this difference is due to the varying density of nerve endings in the skin. On the fingertips, the density of sensory receptors is high, which allows for closer two-point discrimination. In contrast, areas like the palm of the hand, arms, or shoulders have fewer nerve endings, leading to a larger distance required between points to perceive them as distinct stimuli.